Horizontal processing furnaces have been widely used in the fabrication of semiconductor devices. In such furnaces, vapor is introduced at one end of a reactor tube and exhausted at an opposite end. Although a large amount of non-reacted particulate is typically deposited near the exhaust end of the reactor tube, this flaky deposition does not create a major problem in the horizontally oriented system.
For a variety of reasons, including conservation of floor space and increased control of process operations, the semiconductor industry has begun using vertical furnaces in place of horizontal furnaces. In a vertical reactor, process gas(es) (such as TEOS) is (are) typically introduced near the bottom of the reactor and exhausted near the top. As with a horizontally oriented furnace, significant particulate can accumulate near the exhaust end of the reactor, particularly with LPCVD processing where liquid source materials often result in exhaust by-products. However, should deposited by-product break loose in a vertically oriented furnace, the particulate would be pulled gravitationally downward to contaminate the semiconductor wafers (which are typically disposed directly beneath the exhaust port).
Thus, a challenge exists in the art to design an exhaust system for a vertically-oriented furnace which minimizes the likelihood of wafer contamination resulting from non-reacted particulate deposited in the vicinity of the exhaust port breaking free. The present invention addresses this challenge.